There is a need for an in-situ multiple component chemical analyzer to provide periodic measurement of key nutrients and products in mammalian cell culture processes which are conducted in a variety of reactor vessels including roller bottles, T-flasks, shake flasks, spinner bottles, disposable bag bioreactors, and stirred tank bioreactors. At present there is no available instrumentation for in situ monitoring of key nutrients and products in all these vessels during cell culture processes. There have only been initial reports of in situ multi-component analyzers for stirred tank bioreactors using an immersion probe. The new optically based in situ analyzer system would provide a means for simultaneously monitoring several key nutrients and products for cell culture processes conducted both in the small reactor vessels and in stirred tank bioreactors without removing any samples from the vessels. The new multi-component analyzer will find applications in both research and production scale cell culture processes used for producing valuable therapeutic and diagnostic products, including monoclonal antibodies, proteins, and enzymes. The multi- component analyzer would help increase the speed of process development and help optimize the process yields in these cell culture processes through improved process diagnostics and control. [unreadable] [unreadable] [unreadable]